Conventionally, there has been known an optical repeater system (communication relaying system) by which mobile communication terminals such as smartphones are usable indoors.
This optical repeater system causes a plurality of remote units to be connected to one master unit that is connected to a base transceiver station so as to effectively expand a communication area of the base transceiver station. In this manner, a wide range of indoor communication areas such as large-scale commercial facilities and office buildings is covered.
The conventional technique, however, causes output of a low noise amplifier (LNA) prepared for each remote unit to be synthesized as an up signal (uplink signal UL).
Thus, in a master unit, noise is synthesized for the number of remote units, and this processing may cause deterioration in a synthetic noise figure (NF) that is a total noise figure (NF) as a whole optical repeater system.